SEAM DIGGINGS: EL DORADO COUNTY. 115 
§ 14. Seam Diggings. 
At Illinois Cafion, near Georgetown, are so-called “ seam-diggings” which consist of decomposed 
bed-rock, filled with irregular seams ‘of quartz containing gold. This ground is worked by the hy- 
draulic method, and a spot having an area of fifty by a hundred feet has been washed off. This 
operation is said to have paid a little less than wages, on the average, although as high as $40 to 
the pan has been obtained here. 
At Georgia Slide, near Georgetown, they have been working seam diggings in the bed-rock for 
some sixteen or seventeen years, and have reached a depth of 175 feet in the bed-rock, which is a 
rather soft, decomposed slate, generally more or less talcose, and full of decomposed crystals of 
pyrites ; much of the slate itself contains fine gold. 
Young’s Dry Diggings are shallow, surface excavations, covering two or three acres of sloping 
ground, on the southwestern side of the ridge which extends along the road from Georgetown to 
Spanish Dry Diggings. They are said to have paid well, whenever water could be obtained. It is 
stated that a little seam of quartz, some twenty feet long, was once struck here, from which in a 
short time between $ 25,000 and $ 30,000 was taken. The bed-rock at this locality consists partly 
of rather soft slates, and partly of very hard and tough metamorphic sandstones ; the latter occurs, 
in places, in the form of lenticular masses enclosed in the slates. 
The so-called “Spanish Dry Diggings ” belong entirely to the class of “ seam diggings,” although 
the gulches in this vicinity are said to have been rich in the early days. There are two principal 
claims, the “ Grit” and the “Dam.” The course of the main tunnels is very nearly north and 
south, and this appears to be the general course of the belt of rich ground. Immediately east of 
the Grit Claim there is a heavy mass of semi-serpentine, which appears to be a product of the 
metamorphism of a very fine-grained slate. The rocks in the mines are slates and sandstones, the 
latter very fine-grained ; these rocks are filled with crystals of iron pyrites, and traversed by nu- 
merous small irregular seams of quartz. It is said that, in the Grit Claim, the seams which have 
paid best run nearly north and south and dip to the east at an angle of 45°, or thereabouts. These 
seams traverse the decomposed rock and dip towards the serpentine ; but it is stated that they do 
not pass into it. The Grit Claim is said to have yielded not less than $300,000. It was from 
this mine that the magnificent specimen of gold was taken which was on exhibition for some time 
in San Francisco, and which afterwards was taken to Paris. Its intrinsic value was estimated at 
$ 4,000, and it was entirely made up of fine reticulations of imperfect arborescent crystallizations. 
It is said that some $6,000 or $ 8,000 more was taken out from the same place in the immediate 
vicinity of this remarkable specimen. The Dam Claim is said to have yielded $ 250,000 ; and the 
seam diggings, within a mile of the town of Spanish Dry Diggings, have yielded fully $ 1,000,000. 
The small quartz seams in the Dam Claim run in every possible direction, without regularity, 
and the gold is very far from being uniformly distributed through them ; indeed, it occurs chiefly 
in “ pockets,” so that it is commonly said that a miner at these diggings either makes nothing or 
a fortune. It is stated that whenever the quartz seams run into hard rock they thin out or disap- 
pear altogether and the gold almost invariably gives out. 
Immediately opposite Spanish Dry Diggings, on the other side of the river, at a place known as 
Shenanigan Hill, there is a spot where some work has been done, and where there are also seam 
diggings resembling those just described. There are other claims of a similar character in this 
vicinity, and from one — the “Short Handle” — it is said that $ 60,000 was taken, from a seam 
only twenty or twenty-five feet long, and worked to a depth of thirty feet only. 
In the range of hills immediately west and southwest of the village of Greenwood, and which 
rise to the height of from 100 to 150 feet, there are seam diggings of some extent, in the so-called 
Franklin and French Claims. Here a piece of ground of an irregular shape has been worked out, 
covering an area of one or two acres in extent, and the maximum elevation of the banks is about 
sixty or seventy feet. The rocks exposed here are very fine-grained argillaceous slate and sand- 
stones, and associated with these is a rock which was once a fine breccia or conglomerate, and 
